I’m going to keep a running tally of the new Thunder Power eXtreme 2200mAh 3S lipo battery pack I just bought for my Brio 10/Stryker/Super Cub planes and figured here would be as good a place as any to keep record. The charger I have is the Duratrax IntelliPeak Digital Ice. The pack is not discharged in every case before being recharged. Sometimes the pack still has several hundred mAh’s remaining. If time permits, I will run a discharge at 4.40A until the pack reaches 9.00V. Additionally, if time permits I will run a slow charge at 1/2C or 1.1A. Every charge peaks at 12.601V and ends at 0.10A. I have noticed that charging at a rate of <1C does tend to squeak a few more mAh into the pack, however charging at less than 1C has not been proven to prolong battery life (as it does with NiMH/NiCAD cells). The key to long battery life is never discharging at a rate higher than recommended, balancing the pack periodically and never allowing the pack to drop below a specific voltage. In this case, that voltage is 3.00V per cell. Though the actual voltage varies with supplier and user, 3.00V is the safest recommended voltage in my opinion. So that's what I use. I also made a simple, yet safe, connector adapter to monitor each individual cell voltage with a DMM to check for proper balance. After 10 charge/discharge cycles through the ESC leads, the pack is still perfectly matched within 1mV.
Here's some quick stats on the pack:
Thunder Power eXtreme (V2) 2200mAh 25C/50C lithium-polymer 3S 11.1V battery pack
Current capability: 55A continuous/110 peak
Weight: 170g (6.0 0z.)
Size: 107 x 37 x 25mm (4.21 x 1.46 x 0.98in.)
Purchased from: www.CheapBatteryPacks.com on 12-23-2007
Purchase price: $79
Wire gauge: 13AWG (this is some beefy, high-strand count and yet very flexible wire)
Connector used: Deans Ultras
Pack arrived on 12-28-2007
Pack voltage right out of the box = 11.442V (3.814V per cell). The recommended long-term storage of lipos is around 3.85V per cell (see Backyard Flyer, November 2007 issue, pg. 87) or between 3.80V and 3.90V according to TP, so this pack is right in the ball park and obviously hasn’t been sitting around for very long.
Here’s the running data:
Charge #1: Charged at 1.00A for 5013 seconds. Added 1163mAh. 12-28-2007.
Charge #2: Charged at 2.20A for 4903 seconds. Added 1824mAh. 12-29-2007.
Charge #3: Charged at 2.20A for 4582 seconds. Added 2152mAh. 12-29-2007.
Charge #4: Charged at 2.20A for 3330 seconds. Added 1507mAh. 12-29-2007.
Discharged at 4.40A to 3.00V per cell.
Charge #5: Charged at 1.10A for 7906 seconds. Added 2211mAh. 12-30-2007.
Charge #6: Charged at 2.20A for 4343 seconds. Added 2100mAh. 12-30-2007.
Charge #7: Charged at 2.20A for 2670 seconds. Added 1120mAh. 12-30-2007.
Discharged at 4.40A to 3.00V per cell.
Charge #8: Charged at 2.20A for 4688 seconds. Added 2172mAh. 12-31-2007.
Discharged at 4.40A to 3.00V per cell.
Charge #9: Charged at 2.20A for 4871 seconds. Added 2178mAh. 12-31-2007.
Discharged at 4.40A to 3.00V per cell.
Charge #10: Charged at 1.00A for 8599 seconds. Added 2197mAh. 12-31-2007.
Cells monitored for balance: all cells within 0.001V +/- 0.001V accuracy. 1-4-2008.
Charge #11: Charged at 0.50A for 6834 seconds. Added ?mAh. 1-7-2008.
Charge #12: Charged at 2.20A for 2944 seconds. Added 1281mAh. 1-12-2008.
Charge #13: Charged at 2.20A for 3341 seconds. Added 1437mAh. 1-12-2008.
Charge #14: ???
Charge #15: ???
Charge #16: ???
After the novelty of the new pack wore off, I stopped keeping track of every single charge. I guess I just didn’t care that much. Now I just charge and fly. I’ve got about 30 cycles on it so far and it still feels like it’s just as strong as the day I got it. It stays surprisingly balanced too. It is an expensive pack, but I think it’s definitely worth every penny. Though now I’m trying to figure out just which new plane this thing will drop into perfectly.
